I used the Nipple Therapy on a Suzuki GT750 calliper set. Thought I was lost with the restoration, with stripped and sheared nipples. You've rescued what I was starting to think were scrap brakes as replacements are just as badly damaged or made of 'unobtainium'. They look quite good too. Thank you!

All repaired parts are shotblasted, machined and painted. They are made ready for assembly and guaranteed.

Cast Iron Welding Options

Welding Cast Iron

Of all the everyday metals, cast iron is probably the most difficult to repair when it fractures.
The Chinese claim to have invented it centuries ago but it is only in the last century that improved production methods have given us cast iron of consistently good quality and weldability.
The automotive industry is probably the biggest user of cast iron. It is ideal for engine cylinder blocks and heads because it is stable and relatively cheap.
It has two disadvantages:

1. It rusts. All good antifreeze solutions have an anti corrosion additive. Pre war vehicles did not enjoy such luxury. The result is that castings rusted from the inside while the outside remained pristine. When I removed the side of a 20/25 Rolls Royce cylinder head I found the entire coolant space filled with rust flakes. They filled over half of a two gallon bucket.
The sides were so thin they had removed and replaced with panels from a smashed up cast iron bath.

2. It cracks. This happens when the cooling system fails and causes the combustion area to get very hot very quickly. Cast iron does not take kindly to having different temperatures in the same lump and so a crack occurs.

There are four popular ways to repair cast iron.

Metal Stitching.

Said to have been invented in Ancient Egypt, this is a good solution for a range of casting problems. It is done by drilling a series of adjacent holes across a crack.The walls between the holes are broken through and a nickel lock is hammered into the resulting serrated slot. The lock is shaped to match the slot. A lock is fitted every 9/16 inches along the crack.
Between the locks the remaining crack is drilled and tapped to take nickel screws. Each screw interferes with the next one to form a continuous figure of eight.
The whole is then vigorously piened and ground off. Expertly done and painted, the repair is invisible.

The advantage of metal stitching is that it is a cold process. It can often be done in situ with minimal stripping and gives a pressure tight repair.

Disadvantages Not effective on material under 3/16in. thick. No use in combustion areas. The co-efficient of expansion of nickel is different from cast iron so a repair in a hot area will last just as long as it takes your cheque to clear.

Arc Welding.

To understand cast iron welding it is necessary to know that cast iron is more like a currant cake than a plain sponge cake. The currants are lumps of iron oxide which are formed in the casting process. They are inert and cause problems with each of the welding processes.
Arc welding is a fairly instant process. Filler metal is transferred across an electric arc from the end of the filler rod to the parent metal. Any oxides which have been exposed by a weld preparation are covered over by molten metal. There can be no fusion between the molten metal and the area of oxide. This results in a weak weld and an area of porosity.
There is no such thing as a cast iron electrode. There are only electrodes which claim to weld cast iron. These are made of nickel or monel and are used with varying degrees of success.
A welder of average ability measures the quality of his work by lifting one end of a repaired part to waist height and holding it for ten seconds. If the other end does not fall off then that is as good as it gets.
A highly skilled welder using good heat treatment and good quality electrodes can effect some useful repairs but, in the main, most applications are poor and usually fail.
Monel and nickel, being foreign metals, have a different expansion rate to cast iron and this will cause a repair to fail in hot areas.
I am probably biased against arc welding because of the number of times I get second shot at a frost crack after an idiot with a book about arc welding with half of the pages missing.
I have lost count of the number of times a head or block has come to me with a frost crack which could be stitched for £80 except that an arc welding expert has got there first.
Result. A gas welding repair costing hundreds.

Powder Welding.

Popular in America, this method has never caught on here.
The equipment comprises a gas welding torch with a powder hopper. The method is similar to gas welding.
The gas flame is used to preheat the area to be welded. When the the temperature is right a stream of powder is entrained in the flame and deposited in the weld area.
The flame then fuses the powder and more powder is added and fused until the repair is complete.
The result is a homogenous repair of good appearance. The only negative side of this process is that the preferred powder is a nickel alloy with the usual questions about expansion rates.

Gas Welding.

This is the best. The casting to be repaired is preheated and filler rods made of good quality cast iron are used to repair cast iron. The weld pool can be stirred around until the oxides and other impurities float to the surface and get flicked out.
The filler rod has more graphite (carbon) and silicon than the parent metal and this dilutes the molten pool and makes a stronger joint. The cooling is slowed down to at least twelve hours to minimise stresses and hardening.
The casting is then blast cleaned, machined and tested.
Repaired thus, the weld area has no hard spots and can be drilled and tapped as easily as any other part.
I am sometimes asked about the limits to the repairs on cast iron castings using gas welding. I once cut a Ford Escort head in half and welded it together again.
We fitted back on the engine and it worked for years afterwards.
I know this was a stunt but it proved a point and won me a bet.
The product of this process is a stress free casting, machined and tested, with a whole lifetime built back into it. The only downside is that it is a hot, horrible which I would not do if it were not for the satisfaction obtained by transforming a lump of scrap metal into something useful. (and the money).
When I did an 8cwt. ship's head I had to step into the sauna for a while to cool down.

Typical Repairs:

Cracked manifolds. Cracks are ground right out and welded with full penetration. The gasket face is ground flat and it is blasted and painted.

Broken lugs on manifolds. I never weld on broken lugs. I build up a new lug and file and drill to make it new again.

Cylinder heads. Cracks are milled out and welded. Valves, seats, guides and studs are brought up to standard and fully assembled.

Cylinder blocks. Frost cracks and all other damage can be repaired and the block brought up to assembly stage.

If these few words will stop just one person reaching for an arc welder to do an "easy repair" it will be worth it.